Hitherto, since Liquid Crystal Display apparatuses can realize large-sized display screen, light weight, thin structure and/or low power consumption, etc. as compared to Cathode-Ray Tube (CRT), they are used in Television Image Receiver and/or display apparatus for various display purposes along with, e.g., self-light emitting type Plasma Display Panel (PDP), etc. In the liquid crystal display apparatus, liquid crystals are included between two transparent bases (substrates) of various sizes to apply voltage across the transparent electrodes to vary orientation of liquid crystal molecules to change light transmission factor to optically display a predetermined image, etc.
In the liquid crystal display apparatuses, since the liquid crystal itself is not light emitting body, there is provided a backlight unit functioning as a light source, e.g., at the rear face portion of the liquid crystal panel. The backlight unit comprises, e.g., primary light source, light guide plate, reflection film, lens sheet and/or diffusion film, etc. and serves to deliver display light over the entire surface of the liquid crystal panel. In the backlight unit, Cold Cathode Fluorescent Lamp (CCLF) adapted so that mercury or xenon is included within fluorescent tube is used as primary light source. However, it is necessary to solve the problems that light emitting luminance that the cold cathode fluorescent lamp has is low, life time is short and/or low luminance region exists at the cathode side so that uniformity ratio, etc. is bad.
Meanwhile, in liquid crystal display apparatuses of the large size, there is generally provided an Area Litconfiguration Backlight unit in which plural elongated cold cathode fluorescent lamps are disposed at the rear face of the diffusion plate to deliver display light to the liquid crystal panel. Also in such area litconfiguration backlight unit, it is necessary to solve the problems resulting from the above-described cold cathode fluorescent lamp. Particularly, in the case where the area litconfiguration backlight unit is applied to such a large sized television image receiver above 40 inches, the problems of realization of high luminance and realization of high uniformity ratio become more conspicuous.
On the other hand, in the area litconfiguration backlight units, in place of the above-described cold cathode florescent lamp, attention is drawn to backlight of the Light Emitting Diode (hereinafter referred to as LED as occasion may demand) area light type in which a large number of red, green and blue LEDs of light three primary colors are two-dimensionally arranged in the state positioned at the rear face side of the diffusion film to obtain white light. Such LED backlight unit permits reduction of cost with realization of reduction of cost of LED, and permits display of high luminance on large-sized liquid crystal panel by low power consumption.
Moreover, the LED backlight unit is caused to be of the configuration in which a large number of LEDs are mounted on wiring board to diffuse rays of light which have been emitted from the LEDs by diffusion plate to emit the rays of light thus obtained to the liquid crystal panel. Further, in order to efficiently guide light, to the diffusion plate, rays of light which have been emitted from the LEDs disposed at the edge portion of the LED backlight unit, there is provided a reflection plate. Since the reflection plate permits rays of light which have been emitted from the LEDs to be efficiently emitted to the liquid crystal panel, the reflection plate is composed of a bottom surface reflection plate, and forward and backward, and left and right side surface reflection plates.
Meanwhile, in the LED backlight unit, as shown in FIG. 1, respective corner portions where the bottom surface reflection plate and the forward and backward, and left and right side surface reflection plates are connected to each other are furthest apart from LEDs 20A to 20D disposed in the vicinity of these corner portions. In this case, FIG. 2 shows the LEDs 20A to 20D arranged in the vicinity of respective corner portions in an enlarged manner. Since the LEDs 20A to 20D are arranged in this way, in the case where rays of light which have been emitted from the LEDs 20A to 20D arranged in the vicinity of respective corner portions of the LED backlight unit are reflected by the reflection plate, luminance would be lowered as compared to reflected light from LEDs arranged at places except for the portions in the vicinity of the corner portions. When luminance of reflected light is lowered in this way, the corner portion of the liquid crystal panel becomes dark.